Method for thin film formation

ABSTRACT

A method for forming a thin film on a substrate, which comprises aligning an evaporation means for an evaporating material to be deposited on the substrate, a plasma generating zone for dissociating an ion-forming gas into ions and electrons, an ion beam accelerating zone for accelerating the resulting ions and irradiating them onto the substrate, and said substrate on a substantially straight line in the order stated, and depositing a vapor of the evaporating material on the substrate through the plasma generating zone and the ion beam accelerating zone. According to this method, surface irradiation can be carried out uniformly because the ion species and the vapor atoms are irradiated in quite the same direction. Furthermore, the vapor atoms can be activated to a high degree, and the by-product electrons can be effectively utilized for the evaporation of the evaporant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to an improvement in a method for forming a thinfilm comprising a combination of ion beam deposition and vacuumevaporation, and more specifically, to a method and an apparatus forproducing a thin film of high quality, for example a thin high-qualityfilm of boron nitride (to be referred to as BN) of high hardness.

2. Description of the Prior Art

The present inventors previously proposed a novel method for forming athin film comprising a combination of ion irradiation and vacuumdeposition in Japanese Laid-Open Patent Publication No. 2022/1983. Thismethod is directed to the formation of a thin film of a metal compoundon the surface of a substrate by ion beam deposition, in whichaccelerated ions are irradiated onto the substrate, and a vapor of themetal compound is irradiated on the substrate simultaneously oralternately with the irradiation of the ions. According to this method,the evaporant to be deposited is chemically combined with the ions byutilizing the activated evergy or kinetic energy of the accelerated ionsand a new material is formed on the substrate.

FIG. 2 of the accompanying drawings is a schematic view showing atypical apparatus for carrying out this method of thin film formation. Agas to be ionized, for example nitrogen, is introduced into an ionsource 2 via a leak valve 1 and ionized there. The ions are thenaccelerated by an accelerator 3 to impart a predetermined ionaccelerating energy. The ions are then introduced into an analyzermagnet 4 where only the required ion species are magnetically selectedand supplied to a reaction chamber 5.

The reaction chamber 5 is maintained under a high vacuum of 10⁻⁴ torr orless by a vacuum pump 6 (for example, a turbo molecular pump). Asubstrate 7 is fixed to a substrate holder 8 and the selected ionspecies are irradiated on the substrate. In order to irradiate the ionspecies uniformly on the substrate 7, it is desirable to pass the ionspecies through a focusing lens 9.

An evaporation device 10 is disposed below the substrate 7. This deviceis heated by a suitable method, for example by electron beam heating orlaser beam heating. The evaporation device 10 includes an evaporationsource containing B, for example. The amount of the evaporation sourcecontaining B to be deposited and the deposition speed can be measured bya vibratory film thickness tester 11 including a quartz plate, forexample. which is disposed side by side with the holder 8.

The number of atoms of the ion species, i.e. the ionic current, can beaccurately measured by an integrating ammeter 13 having a secondaryelectron repelling electrode 12 annexed to it.

A voltage-adjustable bias power supply 14 is connected between thesubstrate 7 and the secondary electron repelling electrode 12 so that anegative bias voltage is applied to the substrate 7.

In this device, the substrate 7 is set at a predetermined position, andthe inside of the reaction chamber 5 is maintained at a predetermineddegree of vacuum. By operating the evaporation device 10, theevaporation source containing boron is evaporated and deposited in apredetermined amount on the substrate 7. Furthermore, a predeterminedion species is irradiated on it with a predetermined ion accelerationenergy. When at the same time, a predetermined negative bias voltage isapplied to the substrate, a thin film of BN having a high hardness andcomposed mainly of cubic BN (CBN) and hexagonal closed packing BN (WBN)is formed on the surface of the substrate 7.

Since the composition of the thin film to be formed is determined byprescribing the ratio between the ions to be irradiated and thedeposited atoms, thin films of different compositions, for example a BNfilm, can be easily produced by varying this ratio.

In the aforesaid method of thin film formation, the path of the ionatoms to be irradiated toward the substrate 7 from the ion source 2 andthe path of the evaporating atoms to be irradiated toward the substrate7 from the metal vapor evaporating device do not exist in the samedirection. Hence, according to the apparatus shown in FIG. 2, theevaporating atoms are projected at an inclined angle toward thesubstrate 7, and owing to minute raised and depressed portions on thesurface of the substrate 7 or a film-forming surface, shaded parts occurmicroscopically which remain non-irradiated with the evaporated atoms.Uniform surface irradiation is, therefore, impossible.

Furthermore, although it would be easy for the ion atoms to attain ahighly excited level on the substrate 7, the evaporating atoms are notactivated. If, therefore. the evaporating atoms are deposited after theyare caused to gain an activated energy state, the reaction andcombination with the ion atoms can favorably be facilitated.

Furthermore, in the thin-film forming apparatus based on thisconventional method, an ion-forming gas is introduced into a plasmagenerating zone of an ion source to generate ions. During this time, allthe electrons generated simultaneously flow to the ground through thewall surface of the ion source, and consequently, the high energy of theelectrons is wastefully discharged.

SUMMARY OF THE INVENTION

It is an object of this invention to provide a method and an apparatusfor forming a thin film of high quality by a combination of ion beamdeposition and vacuum evaporation, wherein uniform surface irradiationfree from shading is carried out by aligning a path of ion beams and apath of atoms to be deposited in the same direction.

Another object of this invention is to provide a method and an apparatusfor forming a thin film wherein a material to be evaporated anddeposited is activated simultaneously with the formation of high-energyions in ion beam deposition.

Still another object of this invention is to provide a method and anapparatus for forming a thin film wherein electrons generated in an iongenerating zone are also effectively utilized for the evaporation withinthis system of a material to be deposited.

A further object of this invention is to provide a method and anapparatus for forming a thin film of good quality, for example, ahigh-quality thin film of BN having high hardness on a substrate at ahigh speed of film formation.

According to this invention, there is provided a method for forming athin film on a substrate, which comprises aligning an evaporation meansfor an evaporating material to be deposited on the substrate, a plasmagenerating zone for dissociating an ion-forming gas into ions andelectrons, an ion beam accelerating zone for accelerating the resultingions and irradiating them onto the substrate, and said substrate on asubstantially straight line in the order stated, and depositing a vaporof the evaporating material on the substrate through the plasmagenerating zone and the ion beam accelerating zone.

In another aspect, the electrons generated in the plasma-generating zoneare irradiated in the form of beams onto the evaporating material to bedeposited in the aforesaid method.

According to this invention, there is also provided an apparatus forforming a thin film on a substrate, comprising an evaporation means forevaporating an evaporating material to be deposited on the substrate, aplasma generating zone for dissociating an ion-forming gas into ions andelectrons, an ion beam accelerating zone for accelerating the resultingions and irradiating them on the substrate, and a mechanism forsupporting said substrate, said members of the apparatus being alignedon a substantially straight line in the order stated; a extractionelectrode disposed between the plasma generating zone and the ion beamaccelerating zone for extracting the ions to the ion beam acceleratingzone; and an accelerating mechanism provided between the plasmagenerating zone and the evaporation means for accelerating the electronsformed in the plasma generating zone toward the evaporating material tobe deposited.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

FIG. 1 is a schematic view of the thin film forming apparatus of thisinvention; and

FIG. 2 is a schematic view of the conventional thin film-formingapparatus.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The marked characteristic of this invention is that an evaporatingmaterial 16 to be deposited which is held by a holder mechanism 15, aplasma generating zone 17 for dissociating an ion-forming gas into ionsand electrons, an ion beam accelerating zone 19 for accelerating theresulting ions and irradiating them onto a substrate 18, and thesubstrate 18 supported on a supporting mechanism 20 are all aligned on asubstantially straight line in this order, as shown in FIG. 1.

In a plasma generating chamber 29 in FIG. 1, the holding mechanism 15such as a copper hearth containing the evaporating material 16 such asmetallic boron is provided at the bottom, and the plasma generating zone17 exist above it. A gas introducing tube 22 for introduction of theion-forming gas 21 into the plasma generating zone 17 is provided, andaround it are disposed a filament 23 for emitting thermoelectrons and aplasma generating magnet coil 24. An extraction electrode 25 in grid orlattice form, for example, is provided between the plasma generatingzone 17 and the ion beam accelerating zone 19 above it for extractingthe ions generated in the plasma generating zone 17 into theaccelerating zone 19.

An accelerating mechanism, a lens 26 in FIG. 1, is provided in the ionbeam accelerating zone 19 in order to accelerate the extract ions in theform of beams. The lens 26 may be composed of a extracting lens, adecelerating lens and an accelerating lens (not shown) known per seeither alone or in combination. The substrate 18 on which the ions andvapor are irradiated are received within a reaction chamber 27 above theaccelerating zone 19 while it is supported by the supporting mechanism20. At one end of the chamber 27 is provided a gas exhausting port 28connected to a suction vacuum pump (not shown) so as to direct flows ofreacting atoms or molecules in a direction at right angles to thesubstrate.

The substrate 18 and the holder mechanism 15 are connected to a dc powersuppply so that the substrate 18 is of negative polarity and the holdermechanism 15 is of positive polarity. In the illustrated embodiment, thedc power supply 30 is comprised of an ion accelerating variable negativepower supply 30a and an electron accelerating variable positive powersupply 30b which are connected in series to each other through theearth. The plasma generating chamber 29 is grounded through a resistorso as to avoid flow out of electrons, and the ion extraction electrode25 is connected to a variable negative power supply 31 for applying abias voltage which enables ions to be taken out.

An electron focusing magnet coil 32 is disposed between the plasmagenerating zone 17 and the evaporating material 16 for accelerating theelectrons generated in the plasma generating zone in the form of beamstoward the evaporating material 16.

The ion-forming gas 21 introduced through the gas introducing tube 22enters the plasma generating chamber 29 having the plasma generatingzone 17. Then, by emitting thermoelectrons from the filament 23, aplasma is generated, and at the same time, the efficiency of plasmageneration is increased by the plasma generating magnet coil 24. As aresult, the dissociated ions and electrons are produced in the plasmagenerating zone 17.

The resulting ions are taken out of the plasma generating zone 17,namely into the reaction chamber 27 maintained under a high vacuum of10⁻⁴ torr or less by a vacuum pump, by the action of the extractionelectrode 25 to which a negative bias voltage is applied. The ions arefocused and accelerated by the action of the lens 26 and irradiated asaccelerated ion beams onto the substrate 18 to which a negative biasvoltage is applied.

In the present invention, the kinetic energy of the ions is desirablyset at 0.01 KeV to 100 KeV, per atom, preferably 0.1 KeV to 40 KeV peratom. This adjustment makes it easy to form the desired thin filmalthough it depends on the type of the evaporant material.

According to the present apparatus, the electrons generated in theplasma generating zone 17 are used as a source of supply of electronbeams for heating the evaporating material of the vacuum evaporationmeans to be described below.

In the vacuum evaporation means provided in the thin film formingapparatus of this invention, the copper hearth 15 containing themetallic substance 16 to be deposited, for example, B, is provided at apart of the wall surface of the plasma generating chamber 17. A voltageis applied across the copper hearth 16 and the substrate 18 by the dcpower supply 30b so that the copper hearth 16 becomes positive. As aresult, the electrons in the plasma generating zone 17 are irradiated inthe form of beams onto the metallic substance 16 by the electronfocusing magnet coil 32, whereby the metallic substance 16 is heated andbecomes easily evaporable. The evaporated metallic substance, whilebeing highly ionized during passage through the plasma generating zone17, is finally deposited on the substrate 18.

According to the present invention described above, the ion beams andthe evaporating material can be irradiated simultaneously onto thesubstrate in completely the same direction. Hence, uniform surfaceirradiation without shading can be effected, and a thin uniform filmhaving a high quality can be formed.

Furthermore, by irradiating the evaporating material on the substratethrough the plasma generating zone and the ion accelerating zone, theevaporating material can be highly activated, and the reaction of theevaporating material with the ions can be more easily carried out.

Another advantage of the present invention is that the electronsgenerated in the plasma generating zone are effectively utilized for theheating and evaporation of the evaporating material, and therefore theenergy cost can be curtailed, and the structure of the evaporating meanscan be simplified.

Heating of the evaporating material is not limited to the aforesaidembodiment, and may be carried out by laser beam heating or heating by aheater with or without electron beam heating.

The suitable negative voltage (E₁) to be applied to the substrate is-0.01 KV to -20 KV, preferably -0.1 KV to -10 KV. The suitable negativevoltage (E₂) to be applied to the drawing electrode is -0.01 KV to -100KV, preferably -5 KV to -40 KV. The suitable positive voltage to beapplied to the evaporating material is 1 to 20 KV, preferably 4 to 10KV.

For example, a thin film of BN having high hardness may be formed byusing the apparatus described above in the following manner. Thesubstrate 18 is set at a predetermined position, and the inside of thereaction chamber 27 is maintained at a predetermined degree of vacuum.By operating the evaporating means, evaporating atoms are evaporatedfrom the evaporation source 16 containing B, passed through the plasmagenerating zone 17 and deposited in a predetermined amount on thesubstrate 18. At the same time, an ion species at least containingnitrogen is irradiated onto the substrate by a predetermined ionaccelerating energy and simultaneously a predetermined negative bias isapplied to the substrate 18. Consequently, a highly hard thin filmcomposed of BN is formed on the surface of the substrate 18.

It is believed that according to this invention, the ion speciescontaining nitrogen relatively easily attains a high energy level of theSP³ hybridized orbital on the substrate. On the other hand, the boronvapor gains an activated energy state while being ionized during passagethrough the plasma generating zone 17, and is deposited on thesubstrate. Hence, boron becomes easily combined with the nitrogen atomby SP³ bonding.

Furthermore, according to this invention, a path of the nitrogen ionspecies directed toward the substrate is the same as a path of borondirected toward the substrate and both are directed in a directiongenerally perpendicular to the substrate. Hence, uniform surfaceirradiation without shading can be carried out. Thus, the desired highlyhard BN film can be formed efficiently at a high speed of filmformation.

The evaporation source containing boron may be at least one of metallicboron and boron compounds such as boron nitride, boron sulfide,phosphorus boride, hydrogen boride, metallic borides containing aluminumor magnesium and borides of transition metals.

The ion species may be an ion species having a predetermined ionacceleration energy which acts on the evaporation source containing B toform a thin film of BN having high hardness and being composed mainly ofCBN-WBN. Preferably, it is either one of a nitrogen atom ion (N⁺); anitrogen molecule ion (N₂ ⁺); an ion of a nitrogen compound such as anammonia ion (NH₃ ⁺); an ion of a boron compound such as a boron nitrideion (BN⁺); and an inert gas ion such as Ar⁺. B₃ N₃ H₆ or Al₂ B₂ N₄ maybe ionized and used as the ion species. Alternatively, thenitrogen-containing ion species may be used together with such an ionspecies as a boron ion (B⁺) or a hydrogen boride ion (B₂ H₆ ⁺).

Such an ion species is created in the plasma generating zone andsupplied to the surface of the substrate.

The substrate may be of any material such as ceramics, superhard alloys,cermets or various metals or alloys. However, if the substrate is anelectrical insulator, the characteristics of a film deposited thereonwill vary between a charged site and a noncharged site and variations incharacteristics tend to occur easily throughout the film. The substrateis therefore preferably an electric conductor. The electric insulatormay be used if a thin film of an electric conductor is formed on itssurface by a conventional method.

It is important that in the formation of the thin BN film in accordancewith this invention, the ion acceleration energy of the ion speciesshould be 5 to 100 KeV per atom of the ion species.

If the ion acceleration energy of this ion species is less than 5 KeV,the amount of the ion species injected into the deposited film decreasesand the sputtering phenomenon becomes dominant. If it exceeds 100 KeV,the ion species is implanted much deeper than the deposited layer on thesurface of the substrate, and it is difficult to form a highly hard BNfilm composed mainly of CBN or WBN in the deposited layer. Furthermore,the temperature of the deposited layer becomes too high, and theformation fo HBN becomes dominant and a highly hard BN film composedmaily of CBN is difficult to form.

In this embodiment of this invention, the B/N atomic ratio supplied fromthe evaporating source and the ion species is desirably adjusted to arange of from 0.2 to 10, and this leads to the formation of a BN film ofvery high quality. Experiments have shown that the optimum B/N atomicratio is in the range of from 0.5 to 5.

Furthermore, in this embodiment of the invention, in conjunction withthe setting of the ion acceleration energy of the ion species within apredetermined range, the dose rate (the ionic current per unit area ofthe substrate) of the ion species is desirably prescribed such that theamount of heat generated in the substrate by the irradiation of the ionspecies becomes 0.01 to 20 W per cm² of the substrate. If it is exceeds20 W, the temperature of the boron deposited layer becomes too high, andthe formation of HBN becomes dominant, and a highly hard BN filmcomposed of CBN or WBN is difficult to form. On the other hand, if it isless than 0.01 W, the implant and recoil effect and thermal effect bythe ion species cannot be obtained, and it is difficult to synthesizeCBN or WBN.

Preferably, in the present invention, the temperature of the substrateis set at -200° to +700° C.

If the temperature of the substrate is set at -200° to +700° C., ahighly excited state produced locally and instantaneously can be easilymaintained, and the resulting CBN or WBN can be freezed to avoidconversion to HBN. If the temperature of the substrate is less than-200° C., the BN film formed on the substrate surface is liable to peeloff. If it exceeds 700° C., the resulting CBN or WBN is liable to changeto HBN. Experiments have shown that the optimum temperature of thesubstrate is 0° to 400° C.

The following examples illustrate the present invention morespecifically.

EXAMPLE 1

A thin film was formed under the following conditions by using anapparatus of the type shown in FIG. 2.

Evaporating material: metallic boron

Ion-forming gas: nitrogen gas

Substrate: Single crystal silicon

Degree of vacuum in the reaction chamber: 2×10⁻⁵ torr

Ion accelerating negative voltage (E₁): See Table 1

Negative voltage (E₂) applied to the drawing electrode: 35 KV

Positive voltage (E₃) applied to the evaporating material: 4 KV

Temperature of the substrate: See Table 1

When nitrogen gas is used, N₂ ⁺ and N⁺ ions are the main ion species,and the doses of these ions were measured by using a Faraday cup 33a anda calorimeter 33b shown in FIG. 1. The thickness of the film wasmeasured by a film thickness monitor 34 (FIG. 1) based on quartzoscillation.

The B/N atomic ratio was adjusted by changing the electron accelerationvoltage (E₃) and the current to the electron focusing lens 32 andthereby changing the amount of metallic boron evaporated.

The BN composition ratio in the film was determined as follows: The BNcomposition ratio of a sample was determined by the Rutherford's backscattering method. Based on the result obtained, calibration curves withrespect to the measured values in the film thickness monitor, theFaraday cut and the calorimeter were prepared, and the BN compositionratio of the film was then determined from the calibration curves.

The substrate 18 was heated by a ceramic heater (not shown).

The results obtained are summarized in Table 1.

                                      TABLE 1                                     __________________________________________________________________________                    Voltage of the  Speed of                                          Atomic                                                                            Ion accelera-                                                                         negative power                                                                         Temperature                                                                          film Electric                                 Sample                                                                            B/N ting energy                                                                           supply for ion                                                                         of the sub-                                                                          formation                                                                          resistance                                                                          Hardness                           No. ratio                                                                             per ion (KeV)                                                                         acceleration (KV)                                                                      strate (°C.)                                                                  (Å/min.)                                                                       (ohms-cm)                                                                           (Hv; kg/mm.sup.2)                  __________________________________________________________________________     1  12  30      0.01     200    600  .sup. 3 × 10.sup.5                                                            3000                                2  9   30      0.01     200    450  .sup. 2 × 10.sup.9                                                            3500                                3  5   30      0.01     200    360  1.5 × 10.sup.10                                                               5100                                4  2   30      0.01     200    220  2.2 × 10.sup.10                                                               6300                                5  1   30      0.01     200    150  2.4 × 10.sup.10                                                               6900                                6  0.6 30      0.01     200     20  2.9 × 10.sup.10                                                               5400                                7  0.5 30      0.01     200     14  1.6 × 10.sup.13                                                               4800                                8  0.1 30      0.01     200     6     3 × 10.sup.15                                                               4100                                9  1   30      0.1      200    150  --    6900                               10  1   30.5    0.5      200    165  --    7000                               11  1   31.5    1.5      200    180  --    7050                               12  1   32.0    2.0      200    180  --    7100                               13  1   3       0.01     200     6   --    2500                               14  1   10      0.01     200     15  --    3500                               15  1   20      0.01     200     60  --    5200                               16  1   50      0.01     200    160  --    7000                               17  1   100     0.01     200    120  --    6900                               18  1   210     0.01     200    105  --    3100                               19  1   30      0.01      50    180  --    6700                               20  1   30      0.01     400    180  --    6900                               21  1   30      0.01     700    180  --    6500                               22  1   30      0.01     800    180  --    4000                               __________________________________________________________________________

With reference to Table 1, it is noted that samples Nos. 1 to 8 havevarying atomic ratios of B/N, and sample No. 5 having a B/N atomic ratioof 1 shows the largest hardness.

In samples Nos. 9 to 12, the ion acceleration energy per ion becomeslarger as the voltage of the negative power supply for ion accelerationbecomes larger. As a result, the hardness becomes slightly higher, andthe speed of film formation increases.

It is noted with reference to samples 13 to 18 that if the ionacceleration energy is limited within a predetermined range, excellenthardness characteristics can be obtained, and the speed of filmformation can be increased.

With samples Nos. 19 to 22, the hardness characteristics were examinedby varying the temperature of the substrate.

EXAMPLE 2

Production of an AlN film:

An AlN film of high quality was formed by using an apparatus of the typeshown in FIG. 1.

Specifically, a silicon substrate was set at the supporting mechanism20, and the inside of the reaction chamber 27 was evacuated to 2×10⁻⁶torr. Highly pure N₂ gas was introduced into the plasma generatingchamber to form N₂ ⁺ and N⁺ ions. The ions were passed through theaccelerating zone and irradiated onto the substrate. At this time, theelectrons generated in the plasma generating chamber 17 were irradiatedon highly pure Al which is the evaporating material 16, and accelerated.Thus, Al was evaporated. The evaporated Al atoms were highly activatedduring passage through the plasma generating chamber 17 and the ion beamaccelerating zone 19 and deposited on the substrate.

The conditions for the formation of the AlN film were as follows:

Degree of vacuum in the reaction chamber: less than 1×10⁻⁴ torr

Negative voltage for ion acceleration: 2 KV

Ion accelerating energy: 20 KeV

After film formation for one hour, an AlN film having a thickness of9000 Å was obtained.

In this example, the Al atoms were also excited and therefore theresulting AlN film was of high quality and dense. The adhesion of thefilm to the substrate was excellent.

A comb-like electrode was formed in the AlN thin film, and the sonicvelocity of the Rayleigh's waves propagating on its surface was measuredand found to be 5700 m/s. Hence, it was found to have the excellentcharacteristics of an SAW element.

When Ti, Ta, W and Cr were respectively used instead of Al as theevaporating material 16, thin films of highly pure nitrides of therespective metals were obtained.

EXAMPLE 3

Production of an amorphous silicon film:

Example 2 was repeated except that hydrogen gas was used instead of thenitrogen gas, and Si was used instead of Al. By using a mixture ofhydrogen gas and 1 ppm of B₂ H₆ as the doping gas, there was obtained anamorphous silicon film whose valence electron could be controlled.

EXAMPLE 4

Production of a TiC film:

Example 2 was repeated except that a superhard alloy drill was used asthe substrate 18, metallic Ti was used as the evaporating material 16,and methane gas was used as the ion-forming gas 21. The operation wasperformed for 1 hour to coat a TiC film having a thickness of 1micrometer on the drill. During the operation, the drill was vibratorilyrotated.

Ion irradiation increased the nucleus generating density, and fine Ticparticles grew. In addition, since the Ti atoms were deposited in thehighly activated state, the denseness of the resulting film and itsadhesion to the substrate increased. Furthermore, the composition of thefilm was uniform since the two materials were irradiated in the samedirections. It was found that the drill coated in this example had aservice life about twice as long as that obtained by RF ion plating.

EXAMPLE 5

Production of an Al₂ O₃ film:

Example 2 was repeated except tha single crystal silicon was used as thesubstrate 18, metallic Al was used as the evaporating material, andoxygen gas was used as the ion-forming gas 21. By performing theoperation for 1 hour, an Al₂ O₃ film having a thickness of 6000 A wasobtained.

The resulting film was found to have a surface resistance of 10¹²ohms-cm.

When methane gas was used as the ion-forming gas 21 in the aboveprocedure, an Al₄ C₃ film could be formed.

What is claimed is:
 1. A method for forming a thin film on a substrate,comprising the steps of:(i) evaporating a supply of evaporatablematerial to be deposited on the substrate; (ii) introducing anion-forming gas into a plasma generating zone to dissociate theion-forming gas into ions and electrons; (iii) accelerating the ionsresulting from step (ii) in an ion beam accelerating zone andirradiating said accelerated ions onto the substrate; (iv) irradiatingthe electrons resulting from step (ii) onto the supply of evaporatablematerial in the form of beams; (v) arranging the supply of evaporatablematerial, the plasma generating zone, the ion beam accelerating zone andthe substrate in a substantially straight line in the recited order; and(vi) depositing a vapor of the evaporated material on the substratethrough the plasma generating zone and the ion beam accelerating zone.2. The method of claim 1 wherein the ions produced in the plasmagenerating zone are accelerated so that the kinetic energy of the ionsbecomes 0.01 to 100 KeV per atom.
 3. The method of claim 1 wherein theevaporatable material is metallic borom or a boron compound, theion-forming gas is a nitrogen gas or a nitrogen compound gas, and theresulting thin film contains cubic boron nitride, hexagonal close packedboron nitride, or both.
 4. The method of claim 1 wherein a negative biasvoltage is applied to the substrate.
 5. A method for forming a thin filmof boron nitride on a substrate, comprising the steps of:(i) evaporatinga supply of metallic boron to be deposited on the substrate; (ii)introducing nitrogen gas into a plasma generating zone to dissociate thenitrogen gas into nitrogen ions and electrons; (iii) accelerating thenitrogen ions resulting from step (ii) in an ion beam accelerating zoneand irradiating said accelerated nitrogen ions onto the substrate; (iv)irradiating the electrons resulting from step (ii) onto the supply ofmetallic boron in the form of beams; (v) arranging the supply ofmetallic boron, the plasma generating zone, the ion beam acceleratingzone and the substrate in a substantially straight line in the recitedorder; and (vi) depositing a vapor of the evaporated boron on thesubstrate through the plasma generating zone and the ion beamaccelerating zone, to thereby form a thin film of cubic or hexagonalclose packed boron nitride on the substrate.
 6. The method of claim 5,wherein the nitrogen ions produced in the plasma generating zone areaccelerated so that the kinetic energy of the ions becomes 5 to 100 KeVper atom.
 7. A method for forming a thin film of a metal nitride on asubstrate, comprising the steps of:(i) evaporating a supply ofevaporatable material selected from the group consisting of Al, TI, Ta,W and Cr to be deposited on the substrate; (ii) introducing nitrogen gasinto a plasma generating zone to dissociate the nitrogen gas intonitrogen ions and electrons; (iii) accelerating the nitrogen ionsresulting from step (ii) in an ion beam accelerating zone andirradiating said accelerated nitrogen ions onto the substrate; (iv)irrdiating the electrons resulting from step (ii) onto the evaporatablematerial in the form of beams; (v) arranging the supply of evaporatablematerial, the plasma generating zone, the ion beam accelerating zone andthe substrate in a substantially straight line in the recited order; and(vi) depositing a vapor of the evaporated material on the substratethrough the plasma generating zone and the ion beam accelerating zone,to thereby form a thin film of the metal nitride on the substrate.
 8. Amethod for forming a thin film of amorphous silicon on a substrate,comprising the steps of:(i) evaporating a supply of silicon to bedeposted on the substrate; (ii) introducing an ion-forming gascomprising a mixture of hydrogen and doping gas into a plasma generatingzone to dissociate the ion-forming gas into ions and electrons; (iii)accelerating the ions resulting from step (ii) in an ion beamaccelerating zone and irradiating said accelerated ions onto thesubstrate; (iv) irradiating the electrons resulting from step (ii) ontothe supply of silicon in form of beams; (v) arranging the supply ofsilicon, the plasma generating zone, the ion beam accelerating zone andthe substrate in a substantially straight line in the recited order; and(vi) depositing a vapor of the evaporated silicon on the substratethrough the plasma generating zone and the ion beam accelerating zone,to thereby form an amorphous silicon film on the substrate.
 9. A methodfor forming a film on a substrate, comprising the steps of:(i) ionizinga gas to produce positively charged ions of the gas and electrons; (ii)directing the gas ions onto the substrate; (iii) irradiating a supply ofevaporatable material with said electrons to evaporate the material;(iv) ionizing the evaporated material; and (v) directing the ionizedevaporated material onto the substrate to thereby form the film on thesubstrate, the film including atoms of the evaporated material and atomsof the gas.
 10. The method of claim 9, wherein the gas and theevaporated material are ionized in an ionizing zone and directed ontothe substrate by accelerating the gas ions and the ions of theevaporated material through an ion accelerating zone, and wherein thesupply of evaporatable material, the ionizing zone, the ion acceleratingzone and the substrate are disposed in a substantially straight line inthe recited order.
 11. The method of claim 9, wherein the gas ions andthe ions of evaporated material are each directed onto the substrate inthe same direction.